MRI-safe implantable lead assembly

ABSTRACT

A medical device includes a pulse generator and a filter. The pulse generator is configured to generate a stimulation signal and to provide the stimulation signal to tissue of a patient via an implantable lead assembly. The filter is configured to couple to the implantable lead assembly. A combined impedance of the implantable lead assembly and the filter with respect to a current induced by an external electro-magnetic field satisfies an impedance threshold when the external electro-magnetic field has a first frequency and when the external electro-magnetic field has a second frequency. The combined impedance has a peak impedance value when the external electro-magnetic field has a third frequency that is between the first frequency and the second frequency.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. application Ser.No. 14/885,794, filed Oct. 16, 2015, which is hereby incorporated byreference herein in its entirety.

FIELD OF THE DISCLOSURE

The present disclosure is generally related to medical devices andimplantable lead assemblies and, in particular, to medical devices andlead assemblies exposed to MRI fields.

BACKGROUND

Implantable lead assemblies, coupled to medical devices, are used for avariety of medical purposes, such as gathering patient body parameterdata or providing therapy (e.g., electro-stimulation). For example, animplantable lead assembly may be used as part of a system that includesan electrode and a medical device (e.g., an implantable medical deviceor an external medical device). A surgical procedure may be used toimplant at least a portion of the system within tissue of a patient, andremoval of the system from the patient may require a second surgicalprocedure. Accordingly, removal of the system after implantation shouldbe avoided to the extent possible.

If the patient needs certain imaging procedures, such as a magneticresonance imaging (MRI) procedure, after the system is implanted, it maybe preferable to perform the MRI procedure without subjecting thepatient to a surgical procedure to remove the system. However, anelectro-magnetic field used during the MRI procedure can induce electriccurrents in portions of the system, such as the implantable leadassembly. A current induced in an implantable lead assembly by anelectro-magnetic field of an MRI procedure can be dangerous for thepatient. For example, if the current is applied to the tissue of thepatient, the current can cause damage or discomfort.

SUMMARY

Accordingly, an MRI-safe medical device system, lead, or component ofthe present disclosure may be configured to prevent or limit theformation of a current, to dissipate a current, and/or to mitigate theeffects of a current induced in an implantable lead assembly or acomponent thereof by an electro-magnetic field of an MRI procedure. Themedical device system, lead, or component may limit or avoid applicationof the induced current to the tissue of the patient. Additionally, theMRI-safe medical device system, lead, or component may be configured todissipate induced current in a manner that limits formation of localhotspots as a result of Ohmic heating generated by a magnetic field.

During an MRI procedure, an impedance of an implantable lead assembly ofthe medical device system, or a component thereof, may be based on acurrent induced by an electro-magnetic field caused by the MRIprocedure. According to a particular embodiment, the implantable leadassembly may include at least one inductive-capacitive (LC) tank. Theimplantable lead assembly may include a conductor coupled to the LCtank. For example, a portion of the conductor may be wound to form theLC tank. To illustrate, a first section of the conductor may be wound inthe first direction. A second section of the conductor may be wound in asecond direction to overlap a first portion of the first section. Forexample, a second portion of the first section may not be overlapped bythe second section. The second direction may be opposite the firstdirection. A third section of the conductor may be wound in the firstdirection to overlap the second section. A remaining portion of theconductor may be wound in the first direction. The LC tank may includethe overlapping sections (e.g., the first portion of the first section,the second section, and the third section). In a particular embodiment,the implantable lead assembly may exclude the second portion of thefirst section and the remaining portion. For example, the entire lengthof the conductor may form the LC tank.

The LC tank may be formed (e.g., tuned) so that the impedance of theimplantable lead assembly satisfies an impedance threshold (e.g.,approximately 1 kilo-ohm (kOhm)) for an electro-magnetic field that hasa frequency corresponding to a typical MRI frequency. For example, theelectro-magnetic field may induce a current in the implantable leadassembly. The induced current may have a frequency corresponding to thefrequency of the electro-magnetic field. For example, the inducedcurrent may have the same frequency as the electro-magnetic field. Theimpedance of the implantable lead assembly may be greater than or equalto the impedance threshold when a current induced by an externalelectro-magnetic field has a first frequency (e.g., approximately 64megahertz (MHz) or a second frequency (e.g., approximately 124 MHz). Forexample, the impedance of the implantable lead assembly may be greaterthan or equal to the impedance threshold when the externalelectro-magnetic field has the first frequency (e.g., approximately 64megahertz (MHz) corresponding to a 1.5 Tesla (T) MRI system), and may begreater than or equal to the impedance threshold when the externalelectro-magnetic field has the second frequency (e.g., approximately 124MHz corresponding to a 3 T MRI device).

The impedance of the implantable lead assembly may have a peak impedancefor an electro-magnetic field having a third frequency (e.g., afrequency greater than or equal to 90 MHz and less than or equal to 102MHz). The third frequency may be between the first frequency and thesecond frequency. The impedance of the implantable lead assembly maygenerally increase from a first impedance value corresponding to thefirst frequency to the peak impedance corresponding to the thirdfrequency. The impedance of the implantable lead assembly may generallydecrease from the peak impedance to a second impedance valuecorresponding to the second frequency. The first impedance value and thesecond impedance value may be greater than or equal to the impedancethreshold (e.g., approximately 1 kOhm).

The impedance of the implantable lead assembly may have impedance valuesthat are below the impedance threshold for a current having a frequencythat is below the first frequency or greater than the second frequency.For example, a current having a frequency that is below the firstfrequency (or greater than the second frequency) may be generated in theimplantable lead assembly by a pulse generator, e.g., to provide therapyto the patient.

The impedance threshold may be selected such that when exposed to theexternal electro-magnetic field at the first frequency or at the secondfrequency, the implantable lead assembly is able to safely dissipate theinduced current without significant (e.g., greater than 2 degreesCelsius) localized heating. For example, the impedance threshold may beabout 1 kOhm. Thus, in this example, the implantable lead assembly mayhave an impedance of about 1 kOhm with respect to a current induced by a1.5 T MRI system and may have an impedance of about 1 kOhm with respectto a current induced by a 3 T MRI system. Accordingly, a patient withthe implantable lead assembly may safely undergo a 1.5 T MRI procedureor a 3 T MRI procedure without removing the implantable lead assembly.

According to another particular embodiment, the system may include animplantable lead assembly and a medical device. The implantable leadassembly may include a first connector, a second connector, and a firstconductor connecting the first connector and the second connector. Thefirst connector may couple the medical device to the implantable leadassembly, and the second connector may be coupled to an electrode thatmay be placed on and/or implanted within a patient's body.

The medical device may include a header and a housing. In certain cases,the housing may be used to house a pulse generator. The pulse generatormay be configured to generate a stimulation signal and to provide thestimulation signal to tissue of the patient via the implantable leadassembly. In addition, the medical device may include a filter, such asa band-stop filter. The filter may be included within the header or thehousing of the medical device. Furthermore, the filter may be configuredsuch that a combined impedance of the filter and the implantable leadassembly may be tuned based on a current induced by an externalelectro-magnetic field caused by an MRI procedure.

The induced current may have a frequency corresponding to the frequencyof the electro-magnetic field (e.g., the induced current may have thesame frequency as the electro-magnetic field). As such, the filter maybe configured such that the combined impedance of the filter and theimplantable lead assembly may be greater than or equal to an impedancethreshold when the induced current has a first frequency (e.g.,approximately 64 MHz) and/or a second frequency (e.g., approximately 124MHz). For example, the combined impedance may be greater than or equalto the impedance threshold when the external electro-magnetic field hasthe first frequency (e.g., approximately 64 MHz corresponding to a 1.5 TMRI system). The combined impedance may also be greater than or equal tothe impedance threshold when the external electro-magnetic field has thesecond frequency (e.g., approximately 124 MHz corresponding to a 3 T MRIdevice).

Moreover, the filter may be configured such that the combined impedancemay have a peak impedance for an electro-magnetic field having a thirdfrequency (e.g., a frequency greater than or equal to 90 MHz and lessthan or equal to 102 MHz). The third frequency may be between the firstfrequency and the second frequency. The combined impedance of the filterand the implantable lead assembly may generally increase from a firstimpedance value corresponding to the first frequency to the peakimpedance corresponding to the third frequency. The combined impedanceof the filter and the implantable lead assembly may generally decreasefrom the peak impedance to a second impedance value corresponding to thesecond frequency. The first impedance value and the second impedancevalue may be greater than or equal to the impedance threshold (e.g.,approximately 1 kOhm). Thus, the combined impedance may satisfy theimpedance threshold continuously for the entire frequency range betweenthe first frequency and the second frequency.

Further still, the combined impedance may correspond to impedance valuesthat are below the impedance threshold for an induced current (e.g., orthe corresponding electro-magnetic field) having a frequency that isbelow the first frequency or greater than the second frequency. Forexample, an induced current having a frequency that is below the firstfrequency (or greater than the second frequency) may be generated in theimplantable lead assembly by a pulse generator, e.g., to provide therapyto the patient.

The impedance threshold may be selected such that when exposed to theexternal electro-magnetic field at the first frequency or at the secondfrequency (e.g., or any frequency between the first frequency and thesecond frequency), the medical device system is able to safely dissipatethe induced current in the implantable lead assembly without significant(e.g., greater than 2 degrees Celsius) localized heating. For example,the impedance threshold may be about 1 kOhm. Thus, in this example, thefilter and the implantable lead assembly may have a combined impedanceof about 1 kOhm with respect to a current induced by a 1.5 T MRI systemand may have a combined impedance of about 1 kOhm with respect to acurrent induced by a 3 T MRI system. Accordingly, a patient using themedical device system may safely undergo a 1.5 T MRI procedure or a 3 TMRI procedure without removing the implantable lead assembly and/orother components of the medical device system.

Additionally or in the alternative, a tuning circuit may also be coupledto the filter. The tuning circuit may be configured to receive a tuningsignal, and based on the tuning signal, the tuning circuit may beconfigured to adjust the combined impedance of the filter and theimplantable lead assembly. For example, the combined impedance may beadjusted such that the impedance threshold is satisfied when theelectro-magnetic field has a fourth frequency. The fourth frequency maybe outside of the frequency range between the first frequency and thesecond frequency (e.g., the fourth frequency may be less than the firstfrequency or greater than the second frequency). The tuning circuit maybe configured to adjust the combined impedance of the filter and theimplantable lead assembly to satisfy the impedance threshold at anydesired frequency of the induced current and/or the electro-magneticfield.

In another particular embodiment, an implantable lead assembly includesa first conductor and at least one inductive-capacitive (LC) tankcoupled to the first conductor. The first conductor is configured to becoupled to a medical device. An impedance of the implantable leadassembly with respect to a current induced by an externalelectro-magnetic field satisfies an impedance threshold when theexternal electro-magnetic field has a first frequency, satisfies theimpedance threshold when the external electro-magnetic field has asecond frequency, and has a peak impedance value when the externalelectro-magnetic field has a third frequency that is between the firstfrequency and the second frequency.

In another particular embodiment, a system includes a pulse generatorand an implantable lead assembly. The implantable lead assembly includesa conductor configured to be coupled to the pulse generator. At leastone inductive-capacitive (LC) tank is coupled to the first conductor. Animpedance of the implantable lead assembly with respect to a currentinduced by an external electro-magnetic field satisfies an impedancethreshold when the external electro-magnetic field has a firstfrequency, satisfies the impedance threshold when the externalelectro-magnetic field has a second frequency, and has a peak impedancevalue when the external electro-magnetic field has a third frequencythat is between the first frequency and the second frequency

In another particular embodiment, a lead assembly includes a coiledfirst length of wire forming a first section of a coiled conductor. Thelead assembly also includes a coiled second length of the wirecorresponding to at least one LC tank. The at least one LC tank includesa plurality of overlapping windings of the wire. The coiled conductor isformed by coiling the wire along an axis in a first direction. The LCtank is formed by coiling a first portion of the wire in a seconddirection opposite the first direction to form a first overlappingwinding on a portion of the coiled conductor, and by coiling a secondportion of the wire in the first direction to form a second overlappingwinding on the first overlapping winding. The LC tank may include aninsulation layer between adjacent windings.

One particular advantage provided by at least one of the disclosedembodiments is that a patient with an implantable lead assembly maysafely undergo a 1.5 T MRI procedure or a 3 T MRI procedure withoutremoving the implantable lead assembly. For example, the implantablelead assembly may have an impedance of about 1 kOhm with respect to acurrent induced by a 1.5 T MRI system and may have an impedance of about1 kOhm with respect to a current induced by a 3 T MRI system. At animpedance of about 1 kOhm, the implantable lead assembly may safelydissipate the induced current without significant (e.g., greater than 2degrees Celsius) localized heating.

The features, functions, and advantages that have been described can beachieved independently in various embodiments or may be combined in yetother embodiments, further details of which are disclosed with referenceto the following description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a particular embodiment of a system thatuses an implantable lead assembly;

FIG. 2 is a block diagram of another particular embodiment of a systemthat uses an implantable lead assembly and a filter;

FIG. 3 is a block diagram of another particular embodiment of a medicaldevice that uses an implantable lead assembly and a filter;

FIG. 4 is a diagram illustrating impedance characteristics of theimplantable lead assembly of FIG. 1;

FIG. 5 is a diagram of a particular embodiment of the implantable leadassembly of FIG. 1 having an LC tank and a winding configuration;

FIG. 6 is a diagram of another particular embodiment of the implantablelead assembly of FIG. 1 having an LC tank and a winding configuration;

FIG. 7 is a diagram of another particular embodiment of the implantablelead assembly of FIG. 1 having multiple LC tanks and a windingconfiguration;

FIG. 8 is a diagram of another particular embodiment of the implantablelead assembly of FIG. 1 having multiple LC tanks and a windingconfiguration;

FIG. 9 is a diagram of another particular embodiment of the implantablelead assembly of FIG. 1 having multiple LC tanks and a windingconfiguration;

FIG. 10 is a diagram illustrating a winding technique to form an LC tankof the implantable lead assembly of FIG. 1;

FIG. 11 is a diagram illustrating another winding technique to form anLC tank of the implantable lead assembly of FIG. 1;

FIG. 12 is a diagram illustrating another winding technique to form anLC tank of the implantable lead assembly of FIG. 1;

FIG. 13 is a diagram of cross-sections of the implantable lead assemblyof FIG. 1 having an LC tank and a winding configuration; and

FIG. 14 is a diagram of particular embodiments of a conductor of thesystem of FIG. 1 having an LC tank and a winding configuration.

DETAILED DESCRIPTION

Referring to FIG. 1, a system 100 including an implantable lead assembly102 is shown. The implantable lead assembly 102 may be coupled, via afirst connector 110, to a medical device 108 and may be coupled, via asecond connector 112, to an electrode 104. The implantable lead assembly102 may include a conductor 122 extending from a first conductor end 124to a second conductor end 126. The first conductor end 124 may becoupled, via the first connector 110, to the pulse generator 106. Thesecond conductor end 126 may be coupled, via the second connector 112,to the electrode 104.

In a particular embodiment, the system 100, or a portion thereof, may beimplanted within tissue of a patient 140 to provide therapy or to senseinformation from the tissue of the patient 140. For example, theelectrode 104 may be configured to sense information related to tissueof a patient 140 (e.g., electrical signals generated by a nerve of thepatient 140) and to provide the information to the medical device 108via the implantable lead assembly 102. In another example, the electrode104 may be configured to apply an electrical signal from the medicaldevice 108 to the tissue of the patient 140. To illustrate, the medicaldevice 108 may include a pulse generator 106, which may generatestimulation signals that can be applied to the tissue of the patient140, via the implantable lead assembly 102 and the electrode 104, totreat a medical condition of the patient 140. Exemplary medicalconditions that may be treated include a medical disorder, a psychiatricdisorder, a physiological disorder, an involuntary movement disorder, aseizure disorder, a sleep disorder (e.g., apnea or insomnia),depression, a heart disorder, a neurological disorder, a neuro-musculardisorder, a bladder disorder, and obesity.

After the system 100, or a portion of the system 100 (such as theelectrode 104 and at least a portion of the implantable lead assembly102), is implanted within tissue of the patient 140, removing the system100 may require a surgical procedure. To avoid removing the system 100from the patient 140 while the patient 140 undergoes a magneticresonance imaging (MRI) procedure, the implantable lead assembly 102 maybe designed to be MRI safe or MRI resistant. The implantable leadassembly 102 may be configured to safely dissipate currents induced inthe implantable lead assembly 102 by an external electro-magnetic field132 of an MRI system 130.

The implantable lead assembly 102 may be exposed to the externalelectro-magnetic field 132 during a magnetic resonance imaging (MRI)procedure of the patient 140. An impedance of the implantable leadassembly 102 may be based on a current induced within the lead assembly102 or a component thereof by the external electro-magnetic field 132.For example, the impedance of the implantable lead assembly 102 may bebased on a frequency of the induced current. The induced current mayhave the same frequency as the external electro-magnetic field 132. Theimpedance of the implantable lead assembly 102 may satisfy (e.g., may begreater than or equal to) an impedance threshold (e.g., approximately 1kOhm) when the external electro-magnetic field 132 has a first frequency(e.g., approximately 64 megahertz (MHz)) and when the externalelectro-magnetic field has a second frequency (e.g., approximately 128MHz). The first frequency may correspond to a 1.5 T MRI system. Thesecond frequency may correspond to a 3 T MRI system. The impedancethreshold (e.g., approximately 1 kOhm, or greater than or equal to 0.9kilo-ohm (kOhm) and less than or equal to 1.1 kOhm) may include a rangeof impedance values.

The impedance threshold may be selected such that when exposed to theexternal electro-magnetic field 132 having the first frequency or havingthe second frequency, the implantable lead assembly 102 is able tosafely dissipate the induced current without significant (e.g., greaterthan 2 degrees Celsius) localized heating. The implantable lead assembly102 may be MRI-compliant (e.g., magnetic resonance (MR) safe, MRcompatible, or both) for an MRI procedure that uses the first frequencyand/or for an MRI procedure that uses the second frequency.

The implantable lead assembly 102 may have a peak impedance value (e.g.,an anti-resonance value) when the external electro-magnetic field 132has a third frequency (e.g., a frequency greater than or equal toapproximately 90 MHz and less than or equal to approximately 102 MHz),as further described with reference to FIG. 4. The third frequency maybe higher than the first frequency and lower than the second frequency.The implantable lead assembly 102 may include at least oneinductive-capacitive (LC) tank (e.g., an LC tank 120) configured toprovide the implantable lead assembly 102 specific impedance values whenthe assembly 102 is exposed to 1.5 T and/or 3.0 T magnetic fields.

The LC tank 120 may be coupled to the conductor 122. The LC tank 120 maybe formed by winding the conductor 122 (e.g., as further described withreference to FIGS. 5-14). The winding configuration may be selected toprovide the implantable lead assembly 102 the specific impedance valuesdesired when the assembly 102 is exposed to 1.5 T and/or 3.0 T magneticfields. For example, a first section of the conductor 122 may be woundin a first direction (e.g., forward or distally). A second section ofthe conductor 122 may be wound in a second direction (e.g., backward orproximally) to overlap at least a portion of the first section. Thesecond direction may be opposite of the first direction. A third sectionof the conductor 122 may be wound in the first direction to overlap atleast a portion of the second section there by providing a layering oroverlapping of the conductor 122 over itself to form the LC tank 120.The LC tank 120 may include the overlapping sections (e.g., the firstsection, the second section, and the third section) of the conductor122. In a particular embodiment, the conductor 122 may be wound to forma single LC tank (e.g., the LC tank 120). In an alternate embodiment,multiple LC tanks may be coupled to the conductor 122. For example, theLC tank 120 may be coupled to a second LC tank by a portion of theconductor 122.

The LC tank 120 (e.g., formed as described with reference to FIGS. 5-14)may be configured to provide an impedance characteristic or value (or,stated another way, tuned to provide an impedance characteristic orvalue) of the implantable lead assembly 102 so that the impedancesatisfies the impedance threshold when the external electro-magneticfield 132 has a first frequency (e.g., approximately 64 MHz), satisfiesthe impedance threshold when the external electro-magnetic field 132 hasa second frequency (e.g., approximately 128 MHz), and has a peakimpedance value when the external electro-magnetic field 132 has a thirdfrequency (e.g., greater than or equal to 90 MHz and less than or equalto 102 MHz).

The LC tank 120 may include multiple conductive elements, such asdescribed with reference to FIGS. 5-14 that either alone or incombination with the remainder of the conductor 122 windings provide adesired impedance characteristic or value for 1.5 T and/or 3.0 Tmagnetic fields. For example, the LC tank 120 may include overlappingwindings of the conductor 122. The LC tank 120 may include conductiveelements arranged to form a cavity, e.g., as described with reference toFIG. 13. The cavity may include a core (e.g., an air core, a metalliccore, or a non-metallic core). For example, a core insert may bedisposed in the cavity. The core insert may be metallic or non-metallic.The core insert may include at least one of iron, silver, platinum,gold, tungsten, or iridium. The core insert may include a metal alloyincluding at least one of iron, silver, platinum, gold, tungsten, oriridium. The core insert may include iron-platinum (Fe—Pt) pellets.

The implantable lead assembly 102 may direct electrical energy to an LCtank (e.g., the LC tank 120). For example, the implantable lead assembly102 may orient the electrical energy about a core (e.g., a core insert)of the LC tank 120. The electrical energy may be generated by theexternal electro-magnetic field 132. For example, the electrical energymay be generated by a current induced in the implantable lead assembly102 by the external electro-magnetic field 132. The LC tank 120 maydampen the electrical energy so as to limit a temperature increase ofthe implantable lead assembly 102, the electrode 104, tissue in whichthe electrode 104 is implanted, or a combination thereof, to within aparticular temperature (e.g., two degrees Fahrenheit or two degreesCelsius). For example, the LC tank 120 may dissipate at least a portionof the electrical energy to limit the temperature increase when theexternal electro-magnetic field 132 applied by an MRI system 130 has afirst frequency (e.g., approximately 64 MHz) or has a second frequency(e.g., approximately 128 MHz).

The impedance of the implantable lead assembly 102 may be based on acapacitance of the implantable lead assembly 102, an inductance of theimplantable lead assembly 102, a frequency of the externalelectro-magnetic field 132, or a combination thereof. The inductance ofthe implantable lead assembly 102 may be based on inductance fromcoiling of a conductor (e.g., the conductor 122) along the implantablelead assembly 102 including an inductance of one or more LC tankscoupled to the conductor. For example, the impedance of the implantablelead assembly 102 may be based on inductance from coiling of theconductor 122 along the implantable lead assembly 102.

The inductance from the coiling may also be provided by variations inwire material of the conductor 122, a structure (e.g., a silver core) ofthe wire of the conductor 122, a diameter of the wire of the conductor122, a diameter of a coil of the conductor 122, a pitch of the coil ofthe conductor 122, a density of the coil of the conductor 122, a spacingbetween adjacent coils of the conductor 122, quality of insulationbetween adjacent coils of the conductor 122, or a combination thereof.

The inductance of the implantable lead assembly 102 may be provided bythe inductance characteristics arising from the overlapping of aconductor (e.g., the conductor 122) to form an LC tank (e.g., the LCtank 120). The inductance from overlapping may be based on variations inoverlapping (e.g., winding) technique, such as winding techniquesdescribed with reference to FIGS. 5-14. The inductance from overlappingmay be based on a length of an overlap, a length of the LC tank 120, adiameter of a coil (e.g., an inner coil, an outer coil, or both) of theLC tank 120, a degree of symmetry of the LC tank 120, or a combinationthereof.

The inductance of the implantable lead assembly 102 may be provided bythe inductance attributable to a core of an LC tank (e.g., a core of theLC tank 120). The inductance from the core may be based on whether thecore (e.g., a cavity formed by one or more coils) includes air, whetherthe core includes a core insert, material properties (e.g., metallic ornon-metallic) of the core insert, or a combination thereof.

The capacitance of the implantable lead assembly 102 may be provided bya capacitance (e.g., a parasitic capacitance) arising between adjacentportions of coils or from individual coils (e.g., a loop or a series ofloops adjacent or near to another loop or another series of loops). Thecoils, series of coils, or portions of the coils may be horizontally,vertically, or diagonally adjacent to each other. For example, a firstcoil may be between a second coil and a third coil along a particularaxis (e.g., a horizontal axis, a vertical axis, or a diagonal axis). Aportion of the first coil may be adjacent to a portion of the secondcoil. A portion of the first coil may be adjacent to a portion of thethird coil. The capacitance of the implantable lead assembly 102 may beprovided by a parasitic capacitance observed between adjacent portionsof the first coil and the second coil and between adjacent portions ofthe first coil and the third coil.

The capacitance of the implantable lead assembly 102 may be provided bya length of a conductor (e.g., the conductor 122), a number of coils ofthe conductor 122, a density of the coils of the conductor 122, aspacing between the coils of the conductor 122, an insulation materialdisposed between the coils of the conductor 122, or a combinationthereof. The capacitance of the implantable lead assembly 102 may beprovided by one or more material properties of a wire of a conductor(e.g., the conductor 122), a dielectric strength of the conductor 122,or a combination thereof.

The LC tank 120 may be approximately equidistant from the firstconductor end 124 and the second conductor end 126, as illustrated inFIG. 1. In another embodiment, the LC tank 120 may be proximate to thefirst conductor end 124 or proximate to the second conductor end 126. Ina particular embodiment, the LC tank 120 may extend from the firstconductor end 124 to the second conductor end 126.

In a particular embodiment, at least one LC tank (e.g., the LC tank 120)may be proximate to (e.g., included in or included partially in) themedical device 108, the first connector 110, the second connector 112,the pulse generator 106, a battery of the system 100, a hermeticallysealed portion of the pulse generator 106, a hermetically sealed portionof the medical device 108, or another location of the system 100. The LCtank (e.g., the LC tank 120) may operate regardless of whether the pulsegenerator 106 is activated (e.g., powered). In a particular embodiment,at least one LC tank (e.g., the LC tank 120) may be proximate to (e.g.,included in or a portion of) the electrode 104 (e.g., a nerve cuffelectrode). In this embodiment, a heat sink may be proximate to the LCtank (e.g., the LC tank 120). In a particular embodiment, at least oneLC tank (e.g., the LC tank 120) may be external to the medical device108, the first connector 110, the second connector 112, the pulsegenerator 106, a battery of the system 100, or a combination thereof.For example, as illustrated in FIG. 1, the LC tank 120 may be externalto the first connector 110, the second connector 112, the medical device108, and the pulse generator 106.

A coiled implantable lead assembly 102 that includes an LC tank (e.g.,the LC tank 120) may have approximately the same length (e.g., 17inches) as a coiled implantable lead assembly 102 excluding the LC tank.For example, the LC tank 120 may add little or no length to theimplantable lead assembly 102 when the implantable lead assembly 102 iscoiled. As can be appreciated, the length of the conductor forming thelead of the lead assembly 102 and the LC tank portion of the leadassembly 102 may have a conductor length defined to extend from onepoint to another point along the length of the conductor as theconductor forms the loops of the lead assembly 102, with the conductorlength following the length of each loop of the wound conductor. As canalso be appreciated the conductor length can be defined by the overallaxial length of the wound lead assembly or LC tank with the contributionof each looped length disregarded and with each loop contributing anaxial length defining each loops contribution to the axial length of theassembly 102, with that loop axial length being similar to the thicknessof the conductor wire.

An uncoiled implantable lead assembly 102 that includes an LC tank(e.g., the LC tank 120) may be longer than an uncoiled implantable leadassembly 102 that excludes the LC tank, which can be due to the extrawindings and doubling-back configuration of the conductor that may beused to form the LC tank along the length of the conductor. For example,the LC tank 120 may add length to the implantable lead assembly 102 whenthe implantable lead assembly 102 is uncoiled (or stretched). Toillustrate, the implantable lead assembly 102 including the LC tank 120may have a first length (e.g., approximately 400 inches) when theimplantable lead assembly 102 is uncoiled (e.g., stretched). Theimplantable lead assembly 102 excluding the LC tank 120 may have asecond length (e.g., approximately 80 inches) when the implantable leadassembly 102 is uncoiled. The first length may be greater (e.g., morethan twice) the second length. The uncoiled implantable lead assembly102, with or without the LC tank, may have a greater length (e.g.,approximately 80 inches or approximately 400) than a length (e.g.,approximately 17 inches) of the coiled implantable lead assembly 102.

The pulse generator 106 may provide electrical stimulation via theelectrode 104 to tissue of the patient 140. For example, the pulsegenerator 106 may apply a signal, via the implantable lead assembly 102,to tissue of the patient 140. The signal may generate a current in theimplantable lead assembly 102. An impedance of the implantable leadassembly 102 may be based on the current. For example, the impedance ofthe implantable lead assembly 102 may be based on a frequency of thecurrent. The impedance of implantable lead assembly 102 may fail tosatisfy the impedance threshold when the signal is applied to theimplantable lead assembly 102. For example, the frequency of the currentmay be lower than a first frequency (e.g., approximately 64 MHz) orgreater than a second frequency (e.g., approximately 128 MHz). Theimpedance of the implantable lead assembly 102 may be lower than theimpedance threshold when the signal is applied by the pulse generator106. For example, the impedance of the implantable lead assembly 102 mayhave an impedance value that is lower than the impedance threshold whena frequency of the current is lower than the first frequency or when thefrequency of the current is greater than the second frequency. The lowerimpedance value may enable the signal to reach (e.g., provide electricalstimulation to) the tissue of the patient 140.

FIG. 2 illustrates a diagram of a system 200 according to anotherparticular embodiment. The system 200 may include one or more componentsthat are similar and/or that otherwise correspond to components of thesystem 100 illustrated in FIG. 1. To this end, like numbers indicatelike parts with respect to FIG. 1 and FIG. 2. The system 200 may includea medical device 108, and the medical device 108 may include a header202 and a housing 204. The housing 204 may house and/or otherwiseinclude the pulse generator 106. The header 202 may include a headerconnector 206 to connect to the first connector 110 of the implantablelead assembly 102. Additionally or in the alternative, the header 202may include both the header connector 206 and the first connector 110when the implantable lead assembly 102 is coupled to the medical device108. The header 202 may also include a filter 210, which may be coupledto the implantable lead assembly 102, such as via the first connector110. In certain embodiments, the filter 210 may be a band-stop filterthat may be configured to attenuate signals at particular frequenciesand/or particular frequency ranges. Additionally, though FIG. 2 depictsthe filter 210 as being included within the header 202, in otherexamples the filter 210 may be included within other parts of themedical device 108 as well, such as the housing 204 and/or afeed-through area (not pictured) located between the header 202 and thehousing 204. In addition, the filter 210 may also be a component that isinterposed between the first connector 110 and the header 202, and maybe configured to be an interface or an adapter providing a connectionbetween the conductor 112 and the header 202

The filter 210 may include one or more LC circuits and/or LCR circuits.For instance, the filter may include an LC tank, such as LC tank 120. Aspreviously discussed, the inductance of the LC tank may be provided byvariations in overlapping (e.g., winding) technique of a conductor, suchas winding techniques described with reference to FIGS. 5-14. Theinductance from overlapping may be provided by a length of an overlap, alength of the LC tank 120, a diameter of a coil (e.g., an inner coil, anouter coil, or both) of the LC tank 120, a degree of symmetry of the LCtank 120, or a combination thereof. Further, the capacitance of the LCtank 120 may be provided by a capacitance (e.g., a parasiticcapacitance) between adjacent portions of coils formed by the windings.Additionally or in the alternative, the filter 210 may include discreteinductor and/or capacitor components to form the LC and/or LCR circuits.For instance, the inductance of an LC circuit in the filter 210 may beprovided by a discrete inductor or inductors, and the capacitance of theLC circuit may be provided by a discrete capacitor or capacitors, ratherthan relying on a parasitic capacitance such as in the LC tank 120. Inan LCR circuit, the resistance or damping effect may be provided by adiscrete resistor or resistors. In other examples, the LC and/or LCRcomponents (e.g., the inductor(s), capacitor(s), and/or resistor(s)) maybe formed within an integrated circuit. Moreover, the impedance of thefilter 210 may adjustable via a tuning circuit, which may be describedin more detail below with reference to FIG. 3.

As previously discussed, the implantable lead assembly 102 may beexposed to the external electro-magnetic field 132 during a MRIprocedure of the patient 140. The electro-magnetic field 132 may inducea current in the implantable lead assembly 102 or a component thereof,and in certain implementations, both the electro-magnetic field 132 andthe induced current may have the same or approximately the samefrequency. As such, the filter 210 may be configured such that acombined impedance of the filter 210 and the implantable lead assembly102 may satisfy an impedance threshold when the electro-magnetic field132 has a particular frequency and/or has particular frequency within acertain frequency range.

For instance, the combined impedance of the filter 210 and theimplantable lead assembly 102 may satisfy (e.g., may be greater than orequal to) an impedance threshold (e.g., approximately 1 kOhm) when theexternal electro-magnetic field 132 has a first frequency (e.g.,approximately 64 megahertz (MHz)) and when the external electro-magneticfield has a second frequency (e.g., approximately 128 MHz). The firstfrequency may correspond to a 1.5 T MRI system. The second frequency maycorrespond to a 3 T MRI system. The impedance threshold (e.g.,approximately 1 kOhm, or greater than or equal to 0.9 kilo-ohm (kOhm)and less than or equal to 1.1 kOhm) may include a range of impedancevalues.

Further still, the combined impedance may correspond to impedance valuesthat are below the impedance threshold for an induced current (e.g., orthe corresponding electro-magnetic field 132) having a frequency that isbelow the first frequency or greater than the second frequency. Forexample, an induced current having a frequency that is below the firstfrequency (or greater than the second frequency) may be generated in theimplantable lead assembly by the pulse generator 106, e.g., to providetherapy to the patient. Thus, stimulation signals provided by the pulsegenerator 106 may be able to bypass the filter 210. Additionally or inthe alternative, the filter 210 may be disabled (e.g., by a tuningcircuit described in more detail below) while the pulse generator 106generates and/or transmits stimulation signals.

The impedance threshold may be selected such that when exposed to theexternal electro-magnetic field 132 having the first frequency or havingthe second frequency, the filter 210 is able to safely dissipate theinduced current in the implantable lead assembly 102 without significant(e.g., greater than 2 degrees Celsius) localized heating. As a result,the implantable lead assembly 102 may be MRI-compliant (e.g., magneticresonance (MR) safe, MR compatible, or both) for an MRI procedure thatuses the first frequency and for an MRI procedure that uses the secondfrequency.

Furthermore, the combined impedance of the filter 210 and theimplantable lead assembly 102 may correspond to a peak impedance value(e.g., an anti-resonance value) when the external electro-magnetic field132 has a third frequency (e.g., a frequency greater than or equal toapproximately 90 MHz and less than or equal to approximately 102 MHz),as further described with reference to FIG. 4. The third frequency maybe greater than the first frequency and less than the second frequency.

Referring now to FIG. 3, a system 300 is illustrated of a medical device108 that includes a tuning circuit 330. The tuning circuit 330 may becoupled to the filter 210. The tuning circuit 330 may be configured toreceive a tuning signal and adjust, based on the tuning signal, thecombined impedance of the filter 210 and the implantable lead assembly102 to satisfy the impedance threshold at different frequencies. Forinstance, continuing with the previous example, the tuning circuit 330may adjust the combined impedance to satisfy the impedance threshold ata fourth frequency, where the fourth frequency may be outside of thefrequency range between the first frequency and the second frequency.For example, the fourth frequency may be less than the first frequencyor greater than the second frequency.

In other examples, the tuning circuit 330 may be configured to disablethe filter 210 and/or enable bypass of the filter 210. For instance, thetuning circuit 330 may act as a switch for the filter 210 and maydisable the filter 210, such as when stimulation signals are generatedby the pulse generator 106. In yet other examples, the tuning circuit330 may also be configured to adjust the combined impedance of theimplantable lead assembly 102 and the filter 210 according to particularMRI procedures and/or MRI systems. For instance, the tuning circuit 330may adjust the combined impedance to satisfy a different impedancethreshold at different frequencies for a 1.5 T MRI system than for a 3.0T MRI system.

The tuning circuit 330 may be configured to receive the tuning signal inresponse to various indications, such as from a user 340 via a wired orwireless programming signal or a sensor 332 coupled to the implantablelead assembly 102 (e.g., via the first connector 110). For instance, thetuning circuit 330 may be configured to measure an energy value, such asvia the sensor 332, associated with the implantable lead assembly 102.In certain implementations, the energy value may correspond to atemperature of the implantable lead assembly 102. As such, the tuningcircuit 330 may receive the tuning signal in response to the energyvalue satisfying an energy threshold. For instance, the sensor 332 maydetect that the temperature of the implantable lead assembly 102 isgreater than or equal to a particular temperature threshold and providea corresponding indication to the tuning circuit 330. Additionally or inthe alternative, the sensor 332 may be configured to provide periodicenergy value (e.g., temperature) measurements to the tuning circuit 330,and the tuning circuit 330 may perform a determination as to whether theenergy value satisfies the energy threshold.

According to another particular embodiment, the tuning circuit 330 mayreceive the tuning signal in response to a discrete input, such as viaan input terminal 336, from a user 340 of the medical device 108. Forexample, the user 340 may be a medical professional that may wish totune the filter 210 in order to ensure operational safety of the system200 during an MRI procedure performed by a particular MRI machine 130.The medical professional may program the filter 210 by providing one ormore inputs via the input terminal 336. As a result of the input(s), atuning signal may be transmitted to the tuning circuit 330. In responseto receiving the tuning signal, the tuning circuit 330 may adjust thefilter 210 accordingly (e.g., the combined impedance of the filter 210and the implantable lead assembly 102 may be adjusted to satisfy animpedance threshold when the electro-magnetic field 132 reaches aparticular frequency or particular frequencies).

The systems 100, 200, and 300 may enable a safe MRI procedure to beperformed using the implantable lead assembly 102. For example, animpedance of the implantable lead assembly 102 and/or a combinedimpedance of the implantable lead assembly 102 and the filter 210 maysatisfy an impedance threshold when the implantable lead assembly 102 isexposed to the external electro-magnetic field 132 having a firstfrequency during an MRI procedure.

In addition, the systems 100, 200, and 300 may enable a single leadassembly to be used to perform MRI procedures having variousfrequencies. For example, the implantable lead assembly 102 may be usedto perform a first MRI procedure using an external electro-magneticfield having a first frequency or to perform a second MRI procedureusing an external electro-magnetic field having a second frequency. Thefirst frequency may correspond to a 1.5 T MRI system and the secondfrequency may correspond to a 3 T MRI system. A medical professional maythus implant a lead assembly (e.g., the implantable lead assembly 102)in the patient 140 prior to determining whether the patient 140 is toundergo the first MRI procedure or the second MRI procedure.

Furthermore, the medical professional may implant a single lead assembly(e.g., the implantable lead assembly 102) in a patient who is to undergoboth the first MRI procedure and the second MRI procedure. One or morecomponents ((e.g., the implantable lead assembly 102, the medical device108, or both) of the system 100 and 200 may be labeled as MRI safe forthe first frequency and for the second frequency. For example, a surfaceof a component (e.g., the implantable lead assembly 102 or the medicaldevice 108) may include a label (e.g., a pictorial label, a textuallabel, or both) indicating that the component is MRI safe for the firstfrequency, for the second frequency, or for both. The label may indicatethat the component is compatible with a 1.5 T MRI system, a 3 T MRIsystem, or both.

Referring to FIG. 4, a diagram is shown and generally designated at 400.The diagram 400 includes an impedance curve 402. In a particularembodiment, the impedance curve 402 illustrates impedancecharacteristics of the implantable lead assembly 102 of FIG. 1. In theembodiments of FIGS. 1 and 2, for example, the impedance curve 402 canbe based on measured or estimated data or be a representation of theimpedance characteristics built into the lead assembly 102, the LC tank120, and/or components of the assembly 102 by the aforementioned use ofspecific winding configurations and materials that affect impedancecharacteristics. For example, the impedance curve 402 may correspond toimpedance of the implantable lead assembly 102 relative to frequency ofthe external electro-magnetic field 132 of FIG. 1. Impedance of theimplantable lead assembly 102 may be based on a current induced in theimplantable lead assembly 102 by the external electro-magnetic field132. For example, the impedance may be based on a frequency of theinduced current. The frequency of the induced current may be the same asthe frequency of the external electro-magnetic field 132.

The diagram 400 includes a region 420, a region 422, and a region 424.The region 420 may correspond to impedance values of the implantablelead assembly 102 when the external electro-magnetic field 132 has afirst frequency 406 (e.g., approximately 64 MHz). The first frequency406 may correspond to a 1.5 T MRI system. Impedance values within theregion 420 may satisfy an impedance threshold (e.g., approximately 1kOhm) when the external electro-magnetic field 132 has the firstfrequency 406.

The region 422 may correspond to impedance values of the implantablelead assembly 102 when the external electro-magnetic field 132 has asecond frequency 408 (e.g., approximately 128 MHz). The second frequency408 may correspond to a 3 T MRI system. Impedance values within theregion 422 may satisfy the impedance threshold (e.g., approximately 1kOhm) when the external electro-magnetic field 132 has the secondfrequency 408. The region 424 may correspond to peak impedance values ofthe implantable lead assembly 102 when the external electro-magneticfield 132 has a third frequency 410 (e.g., greater than or equal to 90MHz and less than or equal to 102 MHz).

The impedance curve 402 passes through the region 420. For example, theimpedance curve 402 includes a point 414 within the region 420. Thepoint 414 indicates a first impedance of the implantable lead assembly102 when the external electro-magnetic field 132 has the first frequency406 (e.g., approximately 64 MHz). The point 414, within the region 420,indicates that the first impedance satisfies the impedance threshold(e.g., approximately 1 kOhm).

The impedance curve 402 passes through the region 422. For example, theimpedance curve 402 includes a point 416. The point 416 indicates asecond impedance of the implantable lead assembly 102 when the externalelectro-magnetic field 132 has the second frequency 408 (e.g.,approximately 128 MHz). The point 416, within the region 422, indicatesthat the second impedance satisfies the impedance threshold (e.g.,approximately 1 kOhm).

The impedance curve 402 passes through the region 424. For example, theimpedance curve 402 includes a point 418. The point 418 corresponds to apeak impedance value (e.g., an impedance value 412) of the implantablelead assembly 102 when the external electro-magnetic field 132 has athird frequency 410 (e.g., 96 MHz). For example, the impedance value 412may be a maximum impedance value for a particular range of frequencies(e.g., greater than or equal to 15 MHz and less than or equal to 150MHz).

The point 414 (or the point 416) may be determined by measuring thefirst impedance (or the second impedance) of the implantable leadassembly 102 when the external electro-magnetic field 132 has the firstfrequency 406 (or the second frequency 408). In a particular embodiment,the point 414, the point 416, the point 418, or a combination thereof,may be estimated based on a plurality of impedance measurements. Forexample, a plurality of impedance values of the implantable leadassembly 102 corresponding to various frequencies of the externalelectro-magnetic field 132 may be measured. To illustrate, theimplantable lead assembly 102 may include a second conductor coupled toa second electrode attached to the patient 140. The conductor 122, theelectrode 104, the second electrode, and the second conductor may form acircuit between the medical device 108 and a region of tissue to whichthe electrode 104 and the second electrode are attached. The pulsegenerator 106 may apply a measurement signal having a particularfrequency to generate a current in the conductor 122. The measurementsignal used to measure the impedance value may have lower amplitude thana therapy signal used to provide therapy to the patient 140 and may havelower amplitude than a current induced during an MRI procedure. Themeasurement signal may produce little or no electrical energy. Themeasurement signal may be undetectable by the patient 140.

The medical device 108 may measure an impedance value of the implantablelead assembly 102 corresponding to the particular frequency. Forexample, the medical device 108 may measure a voltage differentialbetween the conductor 122 and the second conductor. The medical device108 may determine the impedance value by dividing the voltagedifferential by the generated current. The medical device 108 maydetermine a plurality of impedance values corresponding to variousfrequencies by performing a plurality of impedance measurements. Theimpedance curve 402, or portions thereof, may be generated by curvefitting the plurality of impedance values.

The impedance curve 402 indicates that the impedance of the implantablelead assembly 102 is lower than the impedance threshold 404 (e.g., lessthan approximately 1 kOhm) at a therapy frequency (e.g., a frequencybelow the first frequency 406 or higher than the second frequency 408).The pulse generator 106 of FIG. 1 may apply a signal at the therapyfrequency to provide therapy to the patient 140. The lower impedance mayenable the signal to reach tissue of the patient 140.

An implantable lead assembly (e.g., the implantable lead assembly 102)having impedance characteristics corresponding approximately to theimpedance curve 402 may enable safe MRI procedures to be performed atthe first frequency 406 and at the second frequency 408. In addition,the implantable lead assembly 102 may enable therapy to be performed ata frequency (e.g., 5-300 Hz) below the first frequency 406 or at afrequency (e.g., 433 MHz) higher than the second frequency 408. Forexample, the implantable lead assembly 102 may be used to perform atleast one of low-frequency (LF) therapy, high-frequency (e.g., ultrahigh-frequency (UHF)) therapy, or high-frequency alternating current(HFAC) therapy.

Referring to FIG. 5, a diagram of a particular embodiment of theimplantable lead assembly 102 is shown. The implantable lead assembly102 includes a sheath 502 extending from a first sheath end 504 to asecond sheath end 506. The sheath 502 may be disposed (e.g., wrapped)over the conductor 122. The conductor 122 may include a nickel cobaltalloy disposed over a silver (Ag) layer, as described with reference toFIG. 14.

The sheath 502 may be disposed on at least a portion of the conductor122, and the sheath may be an insulator and/or otherwise configured toprovide a barrier that provides electrical isolation. The sheath 502 maybe disposed over the coiled conductor 122 so as to allow individualadjacent loops of the conductor 122 to electrically communication witheach other within the sheath 502 when one loop abuts an adjacent loop toform an electrical connection between loops in addition to theconnection arising from the loops being formed from a common conductor.The sheath 502 may also be disposed over the conductor wire along thewound length of the conductor to electrically isolate one loop from anadjacent loop thereby maintaining a single electrical pathway along theconductor length from one loop to another without the formation of anelectrical connection between abutting adjacent loops. The first sheathend 504 may also be proximate to the first conductor end 124 of FIG. 1,the second sheath end 506 may be proximate to the second conductor end126 of FIG. 1, or both. For example, a first distance between the firstsheath end 504 and the first conductor end 124 may satisfy (e.g., isless than or equal to) a threshold distance (e.g., 1 inch). A seconddistance between the second sheath end 506 and the second conductor end126 may satisfy (e.g., is less than or equal to) the threshold distance(e.g., 1 inch). To illustrate, the sheath 502 may be disposed on or overthe entire length of the conductor 122.

The first connector 110 of FIG. 1 may be coupled to the first conductorend 124 and to the first sheath end 504. For example, an outer surfaceof the first conductor end 124 may be covered by the first sheath end504 and the covered first conductor end 124 may be coupled to the firstconnector 110. The second connector 112 of FIG. 1 may be coupled to thesecond conductor end 126 and to the second sheath end 506. For example,an outer surface of the second conductor end 126 may be covered by thesecond sheath end 506 and the covered second conductor end 126 may becoupled to the second connector 112.

In a particular embodiment, the first sheath end 504 may be proximate tothe first conductor end 124 (or the second conductor end 126) and thesecond sheath end 506 may be distant from the second conductor end 126(or the first conductor end 124). For example, a first distance betweenthe first sheath end 504 and the first conductor end 124 (or the secondconductor end 126) may satisfy (e.g., is less than or equal to) athreshold distance (e.g., 1 inch). A second distance between the secondsheath end 506 and the second conductor end 126 (or the first conductorend 124) may fail to satisfy (e.g., is greater than) the thresholddistance. To illustrate, the sheath 502 may be disposed on a portion ofthe conductor 122 that has greater proximity to the first conductor end124 (or the second conductor end 126) than to the second conductor end126 (or the first conductor end 124).

In a particular embodiment, the first sheath end 504 may be distant fromthe first conductor end 124 and the second sheath end 506 may be distantfrom the second conductor end 126. For example, each of the firstdistance and the second distance may fail to satisfy the thresholddistance. To illustrate, the sheath 502 may be disposed on a middleportion of the conductor 122. In a particular embodiment, the LC tank120 may be external to the sheath 502. For example, the sheath 502 maybe disposed on a portion of the conductor 122 that excludes the LC tank120.

The sheath 502 may be disposed over or on the LC tank 120. For example,the sheath 502 may be wrapped around a portion of the implantable leadassembly 102 that includes the LC tank 120. As another example, thesheath 502 may be pulled onto the implantable lead assembly 102 to covera portion of the implantable lead assembly 102 that includes the LC tank120. The LC tank 120 may be proximate to the first sheath end 504, thesecond sheath end 506, or both. For example, the LC tank 120 may extendfrom the first sheath end 504 to the second sheath end 506. Toillustrate, the sheath 502 may be disposed on a portion of the conductor122 that corresponds to the LC tank 120. The implantable lead assembly102 may include one or more additional LC tanks that are not covered bythe sheath 502, one or more additional LC tanks that are covered by thesheath 502, or a combination thereof. For example, the implantable leadassembly 102 may include a second conductor and the sheath 502 may alsobe disposed on a portion of the second conductor that corresponds to atleast one additional LC tank.

The sheath 502 may form a protective barrier around at least a portionof the LC tank 120, at least a portion of the conductor 122, or both.For example, the sheath 502 may prevent bodily fluids of the patient 140from contacting at least the portion of the LC tank 120, at least theportion of the conductor 122, or both.

Referring to FIG. 6, a diagram of another particular embodiment of theimplantable lead assembly 102 is shown. The implantable lead assembly102 may include the LC tank 120. The implantable lead assembly 102 mayinclude at least one conductor. For example, the implantable leadassembly 102 may include a first conductor 620 and a second conductor622. The first conductor 620, the second conductor 622, or both, maycorrespond to the conductor 122 of FIG. 1.

The first conductor 620, the second conductor 622, or both, may becoupled to the first connector 110 of FIG. 1. For example, the firstconductor 620, the second conductor 622, or both, may be coupled, viathe first connector 110, to the pulse generator 106 of FIG. 1. Toillustrate, a first conductor end of the first conductor 620 may becoupled via the first connector 110 to the pulse generator 106, a firstconductor end of the second conductor 622 may be coupled via the firstconnector 110 to the pulse generator 106, or both. The first conductor620, the second conductor 622, or both, may be coupled to the secondconnector 112 of FIG. 1. For example, the first conductor 620, thesecond conductor 622, or both, may be coupled, via the second connector112, to the electrode 104 of FIG. 1. To illustrate, a second conductorend of the first conductor 620 may be coupled via the second connector112 to the electrode 104, a second conductor end of the second conductor622 may be coupled via the second connector 112 to the electrode 104, orboth.

The implantable lead assembly 102 may include one or more LC tanks. Forexample, the implantable lead assembly 102 may include the LC tank 120.The LC tank 120 may be coupled to the first conductor 620 and to thesecond conductor 622. For example, the LC tank 120 may include a firstLC tank formed by winding the first conductor 620 (e.g., as describedwith reference to FIGS. 10-12) and may include a second LC tank formedby winding the second conductor 622 (e.g., as described with referenceto FIGS. 10-12). The first LC tank and the second LC tank may be nested(or interleaved) next to each other to reduce an outer diameter of theimplantable lead assembly 102. In a particular embodiment, the first LCtank and the second LC tank may be coupled to distinct electrodes. Forexample, the first conductor 620 and the first LC tank may be coupled,via the second connector 112, to the electrode 104, and the secondconductor 622 and the second LC tank may be coupled, via anotherconnector, to another electrode.

An impedance of the implantable lead assembly 102 may be based on acapacitance of the implantable lead assembly 102, an inductance of theimplantable lead assembly 102, a frequency of the externalelectro-magnetic field 132 of FIG. 1, or a combination thereof. Thecapacitance of the implantable lead assembly 102 may be based on acapacitance of one or more LC tanks of the implantable lead assembly102, a capacitance of one or more conductors of the implantable leadassembly 102, or a combination thereof. For example, the capacitance ofthe implantable lead assembly 102 may be based on a capacitance of theLC tank 120, a capacitance of the first conductor 620, a capacitance ofthe second conductor 622, or a combination thereof.

The inductance of the implantable lead assembly 102 may be based on aninductance of one or more LC tanks of the implantable lead assembly 102,an inductance of one or more conductors of the implantable lead assembly102, or a combination thereof. For example, the inductance of theimplantable lead assembly 102 may be based on an inductance of the LCtank 120, an inductance of the first LC tank, an inductance of thesecond conductor 622, or a combination thereof.

An impedance of the implantable lead assembly 102 including the LC tank120 (or the first LC tank and the second LC tank) may satisfy animpedance threshold when the external electro-magnetic field 132 has afirst frequency and when the external electro-magnetic field 132 has asecond frequency. For example, the implantable lead assembly 102including the LC tank 120 (e.g., formed as described with reference toFIGS. 10-12) may have impedance characteristics as described withreference to FIG. 4. The implantable lead assembly 102 may be thusenable safe MRI procedures at the first frequency or at the secondfrequency.

Referring to FIG. 7, a diagram of another particular embodiment of theimplantable lead assembly 102 is shown. The implantable lead assembly102 may include multiple LC tanks. For example, the implantable leadassembly 102 may include a first LC tank 720 and a second LC tank 722.In a particular embodiment, the implantable lead assembly 102 mayinclude more than two LC tanks. The first LC tank 720 or the second LCtank 722 may correspond to the LC tank 120 of FIG. 1.

One or more of the multiple LC tanks may be disposed at distinctlocations along an axis to improve (e.g., increase) heat dissipation.For example, the first LC tank 720 and the second LC tank 722 may bedisposed at distinct locations along an axis (e.g., horizontal axis (orx-axis) of the implantable lead assembly 102. The first LC tank 720 maybe coupled to a first conductor 724. For example, the first LC tank 720may be formed by winding the first conductor 724 (e.g., as describedwith reference to FIGS. 10-12). The second LC tank 722 may be coupled toa second conductor 726. For example, the second LC tank 722 may beformed by winding the second conductor 726 (e.g., as described withreference to FIGS. 10-12). In a particular embodiment, the implantablelead assembly 102 may include more than two conductors (e.g., the firstconductor 724 and the second conductor 726).

The first conductor 724, the second conductor 726, or both, may becoupled to the first connector 110 of FIG. 1. For example, the firstconductor 724, the second conductor 726, or both, may be coupled, viathe first connector 110, to the pulse generator 106 of FIG. 1. Toillustrate, a first conductor end of the first conductor 724 may becoupled via the first connector 110 to the pulse generator 106, a firstconductor end of the second conductor 726 may be coupled via the firstconnector 110 to the pulse generator 106, or both. The first conductor724, the second conductor 726, or both, may be coupled to the secondconnector 112 of FIG. 1. For example, the first conductor 724, thesecond conductor 726, or both, may be coupled, via the second connector112, to the electrode 104 of FIG. 1. To illustrate, a second conductorend of the first conductor 724 may be coupled via the second connector112 to the electrode 104, a second conductor end of the second conductor726 may be coupled via the second connector 112 to the electrode 104, orboth.

In a particular embodiment, the first LC tank 720 and the second LC tank722 may be coupled to distinct electrodes. For example, the secondconductor end of the first conductor 724 may be coupled via the secondconnector 112 to the electrode 104, and the second conductor end of thesecond conductor 726 may be coupled via another connector to anotherelectrode.

An impedance of the implantable lead assembly 102 including the first LCtank 720 and the second LC tank 722 may satisfy an impedance thresholdwhen the external electro-magnetic field 132 has a first frequency andwhen the external electro-magnetic field 132 has a second frequency. Forexample, the implantable lead assembly 102 including the first LC tank720 (e.g., formed as described with reference to FIGS. 10-12) and thesecond LC tank 722 (e.g., formed as described with reference to FIGS.10-12) may have impedance characteristics described with reference toFIG. 4. The implantable lead assembly 102 may be thus enable safe MRIprocedures at the first frequency or at the second frequency.

Referring to FIG. 8, a diagram of another particular embodiment of theimplantable lead assembly 102 is shown. The implantable lead assembly102 may include multiple LC tanks. For example, the implantable leadassembly 102 may include a first LC tank 828, a second LC tank 830, anda third LC tank 832. In a particular embodiment, the implantable leadassembly 102 may include fewer than three LC tanks or more than three LCtanks. The first LC tank 828, the second LC tank 830, or the third LCtank 832 may correspond to the LC tank 120 of FIG. 1.

An LC tank may be coupled to a plurality of conductors. For example, thefirst LC tank 828, the second LC tank 830, and the third LC tank 832 maybe coupled to the first conductor 724 and to the second conductor 726.For example, the first LC tank 828 may be formed by winding a firstportion of the first conductor 724 and a first portion of the secondconductor 726 (e.g., as described with reference to FIGS. 10-12). Thesecond LC tank 830 may be formed by winding a second portion of thefirst conductor 724 and a second portion of the second conductor 726.The third LC tank 832 may be formed by winding a third portion of thefirst conductor 724 and a third portion of the second conductor 726. Thefirst LC tank 828, the second LC tank 830, and the third LC tank 832 maybe disposed at different locations along an axis (e.g., horizontal axis(or x-axis) of the implantable lead assembly 102 to improve (e.g.,increase) heat dissipation. For example, the first portion, the secondportion, and the third portion of the first conductor 724 (or the secondconductor 726) may correspond to distinct locations of the implantablelead assembly 102. In a particular embodiment, an LC tank may be coupledto fewer than or more than two conductors (e.g., the first conductor 724and the second conductor 726).

An LC tank may include multiple nested LC tanks. For example, the firstLC tank 828 may include a first LC tank nested (or interleaved) with asecond LC tank. The first LC tank may be formed by winding a firstportion of the first conductor 724 (e.g., as described with reference toFIGS. 10-12). The second LC tank may be formed by winding a secondportion of the second conductor 726 (e.g., as described with referenceto FIGS. 10-12). The first portion and the second portion may beinterleaved during winding. The first portion and the second portion maycorrespond to the same location along the implantable lead assembly 102.

An impedance of the implantable lead assembly 102 including the first LCtank 828, the second LC tank 830, and the third LC tank 832 may satisfyan impedance threshold when the external electro-magnetic field 132 hasa first frequency and when the external electro-magnetic field 132 has asecond frequency. For example, the implantable lead assembly 102including the first LC tank 828 (e.g., formed as described withreference to FIGS. 10-12), the second LC tank 830 (e.g., formed asdescribed with reference to FIGS. 10-12), and the third LC tank 832(e.g., formed as described with reference to FIGS. 10-12) may haveimpedance characteristics described with reference to FIG. 4. Theimplantable lead assembly 102 may be thus enable safe MRI procedures atthe first frequency or at the second frequency.

Referring to FIG. 9, a diagram of another particular embodiment of theimplantable lead assembly 102 is shown. The implantable lead assembly102 may include multiple LC tanks (e.g., a first LC tank 934 and asecond LC tank 936). The first LC tank 934 or the second LC tank 936 maycorrespond to the LC tank 120 of FIG. 1. The first LC tank 934 may becoupled to the first conductor 724. For example, the first LC tank 934may be formed by winding a portion of the first conductor 724 (e.g., asdescribed with reference to FIGS. 10-12). The second LC tank 936 may becoupled to the second conductor 726. For example, the second LC tank 936may be formed by winding a portion of the second conductor 726 (e.g., asdescribed with reference to FIGS. 10-12). The implantable lead assembly102 may include the sheath 502. The sheath 502 may be disposed over oron at least a portion of the first conductor 724, at least a portion ofthe second conductor 726, at least a portion of the first LC tank 934,at least a portion of the second LC tank 936, or a combination thereof.

The implantable lead assembly 102 may include a bifurcation point 938.The first conductor 724 may be interleaved with the second conductor 726prior to the bifurcation point 938. The first conductor 724 and thesecond conductor 726 may be bifurcated subsequent to the bifurcationpoint 938. For example, the first conductor 724 and the second conductor726 may not be interleaved subsequent to the bifurcation point 938. In aparticular embodiment, the sheath 502 may be disposed on or over theimplantable lead assembly 102 prior to the bifurcation point 938.

An impedance of the implantable lead assembly 102 including the first LCtank 934 and the second LC tank 936 may satisfy an impedance thresholdwhen the external electro-magnetic field 132 has a first frequency andwhen the external electro-magnetic field 132 has a second frequency. Forexample, the implantable lead assembly 102 including the first LC tank828 (e.g., formed as described with reference to FIGS. 10-12) and thesecond LC tank 830 (e.g., formed as described with reference to FIGS.10-12) may have impedance characteristics described with reference toFIG. 4. The implantable lead assembly 102 may be thus enable safe MRIprocedures at the first frequency or at the second frequency.

FIGS. 10-12 illustrate examples of winding techniques and LC tanks(e.g., the LC tank 120) formed using the winding techniques. FIGS. 10-12are for illustration. It should be understood that in some embodimentsother winding techniques may be used to form an LC tank (e.g., the LCtank 120 of FIG. 1, the first LC tank 720, the second LC tank 722 ofFIG. 7, the first LC tank 828, the second LC tank 830, the third LC tank832 of FIG. 8, the first LC tank 934, or the second LC tank 936 of FIG.9), such as winding techniques used in fabric arts, rope making,weaving, etc. In particular, the winding technique illustrated in FIG. 8can be modified to have a single conductor (first conductor 724) woundwith another material that is not conductive (electrically insulating)or significantly less conductive than first conductor 724. In such aconfiguration illustrated in FIG. 8, the second conductor 726 may beconsidered to be non-conductive or an insulator to provide electricalisolation between each loop formed by the first conductor 724, therebyallowing an uninsulated first conductor 724 to be wound with aninterposed insulator (designated as second conductor 726 in FIG. 8) withor without the use of an insulating coating disposed over the firstconductor 724. As can be appreciated, when the first conductor 724 wrapsover itself to form an LC tank (such as LC tanks 828, 830, and 832) aninsulating sleeve may be interested between the overwrapping layers tomaintain electrical isolation between adjacent or abutting loops offirst conductor 724.

Referring to FIG. 10, a diagram illustrating a winding technique isshown and generally designated 1000. The diagram 1000 includes a windingmap 1002 corresponding to the winding technique, with the winding map1002 illustrating a cross-section view of the wound conductor 724, 726with “x” designating an axial direction of the lead assembly 102 and “y”designating a radial direction extending away from an axis defined bythe lead assembly 102 (not shown). The winding technique may be used toform at least one LC tank of the implantable lead assembly 102. Thewinding map 1002 illustrates a path of a conductor (e.g., the conductor122). For example, the conductor 122 may be wound to follow the pathfrom point 1 to point 18 of the winding map 1002, with points 1-6representing an inner layer, points 7-12 representing a middle layeroverwrapping points 1-6, and points 13-18 representing an outer layeroverwrapping points 7-12 to form the wound conductor configuringproviding the LC tank.

A first portion 1010 of the conductor 122 may be wound (e.g., coiled) ina first direction 1004. For example, coils of the first portion 1010 maycorrespond to point 1-point 6 of the winding map 1002. The coils of thefirst portion 1010 may have a first diameter. The coils of the firstportion 1010 may define a cavity. A core insert may be disposed in thecavity, as described with reference to FIG. 1.

A second portion 1012 may be wound (e.g., coiled) in a second direction1006. The second direction 1006 may be reverse of the first direction1004. The second portion 1012 may overlap the first portion 1010. Coilsof the second portion 1012 may correspond to point 7-point 12 of thewinding map 1002. For example, a first coil 1016 may correspond to point7 of the winding map 1002. The coils of the second portion 1012 may havea second diameter. The second diameter may be larger than the firstdiameter.

A third portion 1014 may be coiled in the first direction 1004. Thethird portion 1014 may overlap the second portion 1012. Coils of thethird portion 1014 may correspond to point 13-point 18 of the windingmap 1002. For example, a second coil 1018 may correspond to point 13 ofthe winding map 1002. The coils of the third portion 1014 may have athird diameter. The third diameter may be larger than the seconddiameter. In a particular embodiment, the first portion 1010, the secondportion 1012, the third portion 1014, or a combination thereof, mayinclude fewer coils or more coils than illustrated in FIG. 10. The LCtank 120 may include the first portion 1010, the second portion 1012,and the third portion 1014. In a particular embodiment, the LC tank 120may include more than three portions.

Referring to FIG. 11, a diagram illustrating a winding technique isshown and generally designated 1100. The diagram 1100 includes a windingmap 1102 corresponding to the winding technique. The winding techniquemay be used to form at least one LC tank of the implantable leadassembly 102. The winding map 1102 illustrates a path of a conductor(e.g., the conductor 122). For example, the LC tank 120 may be formed bywinding the conductor 122 to follow the path from point 1 to point 15 ofthe winding map 1102.

The conductor 122 may be wound (e.g., coiled) in a first direction 1104(e.g., forward). The conductor 122 may be coiled in the first direction1104 to form a coil 1120 and may be coiled around the coil 1120 to forma coil 1122. The coil 1120 may correspond to point 1 of the winding map1102. The coil 1122 may correspond to point 2 of the winding map 1102.The coil 1122 may have a larger diameter than the coil 1120. Theconductor 122 may be wound in the first direction 1104 and may be coiledto form a coil 1124. The coil 1124 may correspond to point 3 of thewinding map 1102. The conductor 122 may be wound in the first direction1104 and coiled to form a coil 1126. The coil 1126 may correspond topoint 4 of the winding map 1102.

The conductor 122 may be wound in a second direction 1106 (e.g.,backward) and may be coiled around the coil 1124 to form a coil 1128.The coil 1128 may correspond to point 5 of the winding map 1102. Thecoil 1128 may have a larger diameter than the coil 1124. The seconddirection 1106 may be reverse of the first direction 1104.

The conductor 122 may be wound in the second direction 1106 and may becoiled around the coil 1122 to form a coil 1130. The coil 1130 maycorrespond to point 6 of the winding map 1102. The coil 1130 may have alarger diameter than the coil 1122.

The conductor 122 may be wound in the first direction 1104 and may becoiled around the coil 1128 to form a coil 1132. The coil 1132 maycorrespond to point 7 of the winding map 1102. The coil 1132 may have alarger diameter than the coil 1128. The conductor 122 may be wound inthe first direction 1104 and may be coiled around the coil 1126 to forma coil 1134. The coil 1134 may correspond to point 8 of the winding map1102. The coil 1134 may have a larger diameter than the coil 1126. Theconductor 122 may be wound in the first direction 1104 and may be coiledto form a coil 1136. The coil 1136 may correspond to point 9 of thewinding map 1102.

One or more coils of the LC tank 120 may define a cavity. For example,the coil 1120, the coil 1126, and the coil 1132 may define a cavity. Acore insert may be disposed in the cavity, as described with referenceto FIG. 1. For example, the core insert may be disposed in one or moreof the coil 1120, the coil 1126, and the coil 1132.

Referring to FIG. 12, a diagram illustrating a winding technique isshown and generally designated 1200. The diagram 1200 includes a windingmap 1202 corresponding to the winding technique. The winding techniquemay be used to form at least one LC tank of the implantable leadassembly 102. The winding map 1202 illustrates a path of a conductor(e.g., the conductor 122). For example, the LC tank 120 may be formed bywinding the conductor 122 to follow the path from point 1 to point 9 ofthe winding map 1202.

The conductor 122 may be wound (e.g., coiled) in a first direction 1204(e.g., forward) to form a coil 1220. The coil 1220 may correspond topoint 1 of the winding map 1202. The conductor 122 may be coiled aroundthe coil 1220 to form a coil 1222 and may be coiled around the coil 1222to form a coil 1224. The coil 1222 and the coil 1224 may correspond topoint 2 and point 3 of the winding map 1202 respectively.

The conductor 122 may be wound in the first direction 1204 and may becoiled to form a coil 1226. The coil 1226 may correspond to point 4 ofthe winding map 1202. The conductor 122 may be coiled around the coil1226 to form a coil 1228 and may be coiled around the coil 1228 to forma coil 1230. The coil 1228 and the coil 1230 may correspond to point 5and point 6 of the winding map 1202 respectively.

One or more of the coils of the conductor 122 may define a cavity. Forexample, the coil 1220 and the coil 1226 may define a cavity. A coreinsert may be disposed in the cavity, as described with reference toFIG. 1.

The LC tank (e.g., the LC tank 120) formed using the winding techniquesdescribed with reference to FIGS. 10-12 may configure the implantablelead assembly 102 to have an impedance that satisfies an impedancethreshold when an external electro-magnetic field 132 has a firstfrequency (e.g., approximately 64 MHz) and satisfies the impedancethreshold when the external electro-magnetic field 132 has a secondfrequency (e.g., approximately 128 MHz). The implantable lead assembly102 including the LC tank 120 may be considered compatible with an MRIsystem corresponding to the first frequency, the second frequency, orboth. For example, the implantable lead assembly 102 may be consideredcompatible with a 1.5 T MRI system, 3 T MRI system, or both.

Referring to FIG. 13, a diagram of cross-sections of the implantablelead assembly 102 is shown and generally designated 1300. The diagram1300 includes an end cross-section and a side cross section of the LCtank 120. The LC tank 120 includes a core 1302. The core 1302 mayinclude an air core, a metallic core, or a non-metallic core. Forexample, a core insert may be disposed in a cavity formed by a coil1304. The core insert may be non-metallic. The core insert may includeat least one of iron, silver, platinum, gold, tungsten, or iridium. Thecore insert may include a metal alloy including at least one of iron,silver, platinum, gold, tungsten, or iridium. The core insert mayinclude iron-platinum (Fe—Pt) pellets.

The coil 1304 may overlap the core 1302. A coil 1306 may overlap thecoil 1304. A coil 1308 may overlap the coil 1306. The coils 1304, 1306,and 1308 may be formed by winding the conductor 122 of FIG. 1, e.g., asdescribed with reference to FIGS. 10-12.

Referring to FIG. 14, a diagram of particular embodiments of a conductoris shown and generally designated 1400. The diagram 1400 illustratescross-sections of a conductor 1422, a conductor 1424, and a conductor1426. The conductor 1422, the conductor 1424, or the conductor 1426 maycorrespond to one or more conductors of the implantable lead assembly102 of FIG. 1. For example, the conductor 1422, the conductor 1424, orthe conductor 1426 may correspond to the conductor 122 of FIG. 1.

The conductor 1422 may include a first layer 1404, a second layer 1406,and an insulation layer 1408. The first layer 1404 may include aconductor. The first layer 1404 may include a metal or a metal alloy.For example, the first layer 1404 may include at least one of silver(Ag), copper (Cu), gold (Au), or aluminum (Al). A particular metal maybe selected to form the first layer 1404 based on thermal conductivityof the particular metal, cost of the particular metal, or both. Forexample, silver may have higher thermal conductivity than copper. Coppermay be more cost-effective than silver. The second layer 1406 may bedisposed on or over the first layer 1404. The second layer 1406 mayinclude a nickel cobalt alloy. The nickel cobalt alloy may becorrosion-resistant. The insulation layer 1408 may be an insulationcoating disposed on or over the second layer 1406. An LC tank (e.g., theLC tank 120 of FIG. 1) formed by winding the conductor 1422 may includetwo insulating layers between adjacent windings (or coils). For example,the insulation layer 1408 of a first coil and the insulation layer 1408of a second coil may be between the first coil and the second coil whenthe first coil is adjacent to the second coil.

The conductor 1424 may include the second layer 1406 disposed on or overthe first layer 1404. The insulation layer 1408 may be disposed betweenadjacent coils of the conductor 1422. An LC tank (e.g., the LC tank 120of FIG. 1) formed by winding the conductor 1424 may include a singleinsulating layer (e.g., the insulation layer 1408) between adjacentwindings (or coils).

The conductor 1426 includes the second layer 1406 on one side and theinsulation layer 1408 on the opposite side. The conductor 1426 may bewound to form the LC tank 120 such that the insulation layer 1408 of onewinding overlaps the second layer 1406 of an adjacent winding. An LCtank (e.g., the LC tank 120 of FIG. 1) formed by winding the conductor1424 may include a single insulating layer (e.g., the insulation layer1408) between adjacent windings (or coils). The conductor 1426 may havea shape (e.g., a flat tape-like shape) such that the conductor 1426assumes an orientation during winding. The insulation layer 1408 may beplaced on the conductor 1426 based on the orientation so that when theconductor 1426 is wound (e.g., as described with reference to FIGS.10-12) to form the LC tank 120, the insulation layer 1408 separatesadjacent coils or windings of the conductor 1426.

The insulation layer 1408 may be added during winding of a conductor(e.g., the conductor 1422, the conductor 1424, or the conductor 1426) toform the LC tank 120. The insulation layer 1408 may be a separatestructure from the conductor (e.g., the conductor 1422, the conductor1424, or the conductor 1426). For example, the insulation layer 1408 maybe disposed on a first coil (or a first winding) of the LC tank 120prior to overlapping the first coil (or the first winding) with a secondcoil (or a second winding). The insulation layer 1408 may be a viscousliquid that is added during winding of the conductor (e.g., theconductor 1422, the conductor 1424, or the conductor 1426).

The insulation layer 1408 may prevent current from skipping from coil tocoil of the LC tank 120. The conductor (e.g., the conductor 1422, theconductor 1424, or the conductor 1426) may have a parasitic capacitancebetween a first coil and a second coil separated by the insulation layer1408.

Although the description above contains many specificities, thesespecificities are utilized to illustrate some of the exemplaryembodiments of this disclosure and should not be construed as limitingthe scope of the disclosure. The scope of this disclosure should bedetermined by the claims, their legal equivalents. A method or devicedoes not have to address each and every problem to be encompassed by thepresent disclosure. All structural, chemical and functional equivalentsto the elements of the disclosure that are known to those of ordinaryskill in the art are expressly incorporated herein by reference and areintended to be encompassed by the present claims. A reference to anelement in the singular is not intended to mean one and only one, unlessexplicitly so stated, but rather it should be construed to mean at leastone. No claim element herein is to be construed under the provisions of35 U.S.C. § 112, sixth paragraph, unless the element is expresslyrecited using the phrase “means for.” Furthermore, no element, componentor method step in the present disclosure is intended to be dedicated tothe public, regardless of whether the element, component or method stepis explicitly recited in the claims.

The disclosure is described above with reference to drawings. Thesedrawings illustrate certain details of specific embodiments thatimplement the systems and methods of the present disclosure. However,describing the disclosure with drawings should not be construed asimposing on the disclosure any limitations that may be present in thedrawings. The present disclosure contemplates methods, systems andprogram products on any machine-readable media for accomplishing itsoperations. The embodiments of the present disclosure may be implementedusing an existing computer processor, or by a special purpose computerprocessor incorporated for this or another purpose or by a hardwiredsystem.

As noted above, embodiments within the scope of the present disclosureinclude program products comprising computer readable storage device, ormachine-readable media for carrying, or having machine-executableinstructions or data structures stored thereon. Such machine-readablemedia can be any available media which can be accessed by a generalpurpose or special purpose computer or other machine with a processor.By way of example, such machine-readable media can comprise RAM, ROM,EPROM, EEPROM, CD ROM or other optical disk storage, magnetic diskstorage or other magnetic storage devices, or any other medium which canbe used to carry or store program code in the form of machine-executableinstructions or data structures and which can be accessed by a generalpurpose or special purpose computer or other machine with a processor.The disclosure may be utilized in a non-transitory media. Combinationsof the above are also included within the scope of machine-readablemedia. Machine-executable instructions comprise, for example,instructions and data which cause a general purpose computer, specialpurpose computer, or special purpose processing machines to perform acertain function or group of functions.

Embodiments of the disclosure are described in the general context ofmethod steps which may be implemented in one embodiment by a programproduct including machine-executable instructions, such as program code,for example, in the form of program modules executed by machines innetworked environments. Generally, program modules include routines,programs, objects, components, data structures, etc., that performparticular tasks or implement particular abstract data types.Machine-executable instructions, associated data structures, and modulesrepresent examples of program code for executing steps of the methodsdisclosed herein. The particular sequence of such executableinstructions or associated data structures represent examples ofcorresponding acts for implementing the functions described in suchsteps.

Embodiments of the present disclosure may be practiced in a networkedenvironment using logical connections to one or more remote computershaving processors. Logical connections may include a local area network(LAN) and a wide area network (WAN) that are presented here by way ofexample and not limitation. Such networking environments are commonplacein office-wide or enterprise-wide computer networks, intranets and theInternet and may use a wide variety of different communicationprotocols. Those skilled in the art will appreciate that such networkcomputing environments will typically encompass many types of computersystem configurations, including personal computers, hand-held devices,multi-processor systems, microprocessor-based or programmable consumerelectronics, network PCs, servers, minicomputers, mainframe computers,and the like. Embodiments of the disclosure may also be practiced indistributed computing environments where tasks are performed by localand remote processing devices that are linked (either by hardwiredlinks, wireless links, or by a combination of hardwired or wirelesslinks) through a communications network. In a distributed computingenvironment, program modules may be located in both local and remotememory storage devices.

An exemplary system for implementing the overall system or portions ofthe disclosure might include a general purpose computing device in theform of a computer, including a processing unit, a system memory, and asystem bus that couples various system components including the systemmemory to the processing unit. The system memory may include read onlymemory (ROM) and random access memory (RAM). The computer may alsoinclude a magnetic hard disk drive for reading from and writing to amagnetic hard disk, a magnetic disk drive for reading from or writing toa removable magnetic disk, and an optical disk drive for reading from orwriting to a removable optical disk such as a CD ROM or other opticalmedia. The drives and their associated machine-readable media providenonvolatile storage of machine-executable instructions, data structures,program modules, and other data for the computer.

It should be noted that although the flowcharts provided herein show aspecific order of method steps, it is understood that the order of thesesteps may differ from what is depicted. Also two or more steps may beperformed concurrently or with partial concurrence. Such variation willdepend on the software and hardware systems chosen and on designerchoice. It is understood that all such variations are within the scopeof the disclosure. Likewise, software and web implementations of thepresent disclosure could be accomplished with standard programmingtechniques with rule based logic and other logic to accomplish thevarious database searching steps, correlation steps, comparison stepsand decision steps. It should also be noted that the word “component” asused herein and in the claims is intended to encompass implementationsusing one or more lines of software code, and/or hardwareimplementations, and/or equipment for receiving manual inputs.

The foregoing descriptions of embodiments of the disclosure have beenpresented for purposes of illustration and description. It is notintended to be exhaustive or to limit the disclosure to the precise formdisclosed, and modifications and variations are possible in light of theabove teachings or may be acquired from practice of the disclosure. Theembodiments were chosen and described in order to explain the principalsof the disclosure and its practical application to enable one skilled inthe art to utilize the disclosure in various embodiments and withvarious modifications as are suited to the particular use contemplated.

The illustrations of the embodiments described herein are intended toprovide a general understanding of the structure of the variousembodiments. The illustrations are not intended to serve as a completedescription of all of the elements and features of apparatus and systemsthat utilize the structures or methods described herein. Many otherembodiments may be apparent to those of skill in the art upon reviewingthe disclosure. Other embodiments may be utilized and derived from thedisclosure, such that structural and logical substitutions and changesmay be made without departing from the scope of the disclosure. Forexample, method steps may be performed in a different order than isshown in the figures or one or more method steps may be omitted.Accordingly, the disclosure and the figures are to be regarded asillustrative rather than restrictive.

Moreover, although specific embodiments have been illustrated anddescribed herein, it should be appreciated that any subsequentarrangement designed to achieve the same or similar results may besubstituted for the specific embodiments shown. This disclosure isintended to cover any and all subsequent adaptations or variations ofvarious embodiments. Combinations of the above embodiments, and otherembodiments not specifically described herein, will be apparent to thoseof skill in the art upon reviewing the description.

The Abstract of the Disclosure is submitted with the understanding thatit will not be used to interpret or limit the scope or meaning of theclaims. In addition, in the foregoing Detailed Description, variousfeatures may be grouped together or described in a single embodiment forthe purpose of streamlining the disclosure. This disclosure is not to beinterpreted as reflecting an intention that the claimed embodimentsrequire more features than are expressly recited in each claim. Rather,as the following claims reflect, the claimed subject matter may bedirected to less than all of the features of any of the disclosedembodiments.

What is claimed is:
 1. An implantable lead comprising: a conductorhaving a conductor length extending from a first end to a second end ofthe conductor; a sheath having a sheath length extending from a firstend to a second end of the sheath, the sheath disposed over theconductor from the conductor first end to the conductor second end; andopposing first and second lead ends, the first lead end coupled to thefirst ends of the conductor and sheath and the second lead end coupledto the second ends of the conductor and sheath, wherein the conductorhas a first portion at the first end of the conductor and a secondportion at the second end of the conductor and an inductor-capacitorportion disposed between the first and second portions, the first andsecond portions having a single length of the conductor disposed withinthe sheath, the inductor-capacitor portion having at least three lengthsof the conductor disposed proximate to each other to define an LC tank,the LC tank being tuned to resonate at a frequency of approximately90-102 MHz when exposed to a first external magnetic field having afirst frequency of 64 MHz and a second external magnetic field having asecond frequency of 128 MHz, the LC tank being further tuned to provideapproximately 1 kOhm of impedance when exposed to the first externalmagnetic field and the second external magnetic field.
 2. Theimplantable lead of claim 1, wherein at least one of the at least threelengths is configured as a coiled winding that defines a core of theinductor-capacitor portion.
 3. The implantable lead of claim 2, whereinanother one of the at least three lengths is disposed at the core. 4.The implantable lead of claim 2, wherein the inductor-capacitor portionis configured to define a cavity at the core.
 5. The implantable lead ofclaim 2, the implantable lead further comprising a non-metallic coreinsert disposed at the core.
 6. The implantable lead of claim 2, theimplantable lead further comprising a metallic core insert disposed atthe core, the core insert including Fe-PT pellets.
 7. The implantablelead of claim 2, the implantable lead further comprising a metallic coreinsert disposed at the core, the metallic core including at least one ofiron, platinum, gold, tungsten, and iridium.
 8. The implantable lead ofclaim 1, wherein the conductor includes an inner layer encased by anouter layer, the inner layer comprising silver and the outer layercomprising a nickel cobalt alloy.
 9. An implantable lead comprising: aconductor having a conductor length extending from a first end to asecond end of the conductor, the conductor further having a straightportion coupled to an inductor-capacitor portion, the straight portionhaving a straight length of the conductor, the inductor-capacitorportion having a coiled length of the conductor defining an internalcore of the inductor-capacitor portion; and a core insert disposed atthe internal core, wherein the inductor-capacitor portion and the coreinsert together define an LC tank, the LC tank being tuned to resonateat a frequency of approximately 90-102 MHz when exposed to a firstexternal magnetic field having a frequency of 64 MHz and a secondexternal magnetic field having a frequency of 128 MHz, the LC tank beingfurther tuned to provide approximately 1 kOhm of impedance when exposedto the first external magnetic field and the second external magneticfield.
 10. The implantable lead of claim 9, wherein the coiled length isoverwrapped by an additional length of the conductor.
 11. Theimplantable lead of claim 10, wherein at least a portion of theadditional length is coiled.
 12. The implantable lead of claim 11,wherein the coiled length is intertwined with an additional length ofthe conductor.
 13. The implantable lead of claim 12, wherein at least aportion of the additional length is coiled.
 14. The implantable lead ofclaim 9, wherein the core insert is metallic.
 15. The implantable leadof claim 14, wherein the metallic core includes at least one of iron,platinum, gold, tungsten, and iridium.
 16. The implantable lead of claim15, wherein the core insert includes Fe-PT pellets.
 17. The implantablelead of claim 9, wherein the conductor includes an inner layer encasedby an outer layer, the inner layer comprising silver and the outer layercomprising a nickel cobalt alloy.
 18. An implantable medical devicecomprising: a pulse generator having a port; and a lead coupled to theport, the lead comprising: a conductor having a conductor lengthextending from a first end to a second end of the conductor, theconductor further having a straight portion coupled to aninductor-capacitor portion, the straight portion having a straightlength of the conductor, the inductor-capacitor portion having a coiledlength of the conductor defining an internal core of theinductor-capacitor portion, and a core insert disposed at the internalcore, wherein the inductor-capacitor portion and the core inserttogether define an LC tank, the LC tank being tuned to resonate at afrequency of approximately 90-102 MHz when exposed to a first externalmagnetic field having a frequency of 64 MHz and a second externalmagnetic field having a frequency of 128 MHz, the LC tank being furthertuned to provide approximately 1 kOhm of impedance when exposed to thefirst external magnetic field and the second external magnetic field.19. The implantable medical device of claim 18, the pulse generatorincluding a damping circuit configured to dampen electrical energyimparted to the conductor by the external magnetic field.
 20. Theimplantable medical device of claim 18, further comprising labelingdescribing the implantable medical device as MRI safe.